Method and apparatus for measuring eccentricity in rotation of a disc in a disc drive system

Abstract

Some of the embodiments of the present disclosure provide a method for operating a disc drive system, the method comprising based at least in part on a first injector signal, oscillating a focusing apparatus of the disc drive system; while oscillating the focusing apparatus of the disc drive system and rotating a disc placed within the disc drive system, estimating an amplitude of a track crossing speed signal; generating a second injector signal having a frequency that is substantially the same as a frequency of the first injector signal; and based at least in part on the estimated amplitude of the track crossing speed signal and the second injector signal, estimating a sign of the track crossing speed signal.

What is claimed is: 
     
       1. A method for operating a disc drive system, the method comprising:
 based at least in part on a first injector signal, oscillating a focusing apparatus of the disc drive system; 
 while oscillating the focusing apparatus of the disc drive system and rotating a disc placed within the disc drive system, estimating an amplitude of a track crossing speed signal; 
 generating a second injector signal having a frequency that is substantially the same as a frequency of the first injector signal; 
 based at least in part on the estimated amplitude of the track crossing speed signal and the second injector signal, estimating a sign of the track crossing speed signal, wherein the track crossing speed signal comprises a low frequency component that is substantially due to the eccentricity of the disc and a high frequency component that is substantially due to the oscillation of the focusing apparatus; 
 filtering the track crossing speed signal using a band pass filter such that an output of the band pass filter substantially comprises the high frequency component of the track crossing speed signal; 
 multiplying the output of the band pass filter with the second injector signal to generate a multiplication signal; and 
 filtering the multiplication signal using a low pass filter to generate a sign detection signal, 
 wherein the sign detection signal provides an indication of the sign of the track crossing speed signal. 
 
     
     
       2. The method of  claim 1 , further comprising:
 based at least in part on the estimated amplitude and the estimated sign of the track crossing speed signal, estimating an eccentricity signal, wherein the eccentricity signal measures an eccentricity of the disc while the disc rotates within the disc drive system. 
 
     
     
       3. The method of  claim 2 , further comprising:
 in response to estimating the eccentricity signal, performing an acquisition and tracking of a track of the disc by the focusing apparatus. 
 
     
     
       4. The method of  claim 1 , wherein oscillating the focusing apparatus of the disc drive system further comprises:
 oscillating the focusing apparatus of the disc drive system using the first injector signal such that the frequency of the first injector signal is substantially higher than a frequency of rotation of the disc within the disc drive system. 
 
     
     
       5. The method of  claim 1 , wherein the track crossing speed signal refers to a speed with which tracks of the disc cross the focusing apparatus while the disc is rotating within the disc drive system, when viewed from the focusing apparatus. 
     
     
       6. The method of  claim 1 , wherein the track crossing speed signal refers to a speed with which tracks of the disc cross a focal point of a light beam generated by the focusing apparatus while the disc is rotating within the disc drive system, when viewed from the focusing apparatus. 
     
     
       7. A method for operating a disc drive system, the method comprising:
 based at least in part on a first injector signal, oscillating a focusing apparatus of the disc drive system; 
 while oscillating the focusing apparatus of the disc drive system and rotating a disc placed within the disc drive system, estimating an amplitude of a track crossing speed signal; 
 generating a second injector signal having a frequency that is substantially the same as a frequency of the first injector signal; 
 based at least in part on the estimated amplitude of the track crossing speed signal and the second injector signal, estimating a sign of the track crossing speed signal, wherein the track crossing speed signal comprises a low frequency component that is substantially due to the eccentricity of the disc and a high frequency component that is substantially due to the oscillation of the focusing apparatus; 
 filtering the track crossing speed signal using a band pass filter such that an output of the band pass filter substantially comprises the high frequency component of the track crossing speed signal; 
 filtering the track crossing speed signal using a low pass filter such that an output of the low pass filter substantially comprises the low frequency component of the track crossing speed signal; and 
 based at least in part on the output of the low pass filter and the estimated sign of the track crossing speed signal, determining an eccentricity signal, wherein the eccentricity signal measures an eccentricity of the disc while the disc rotates within the disc drive system. 
 
     
     
       8. The method of  claim 7 , wherein the estimated sign of the track crossing speed signal is determined prior to reading from or writing to a track of the disc. 
     
     
       9. The method of  claim 7 , further comprising:
 generating, using a digital time oscillator, a digital signal having a periodicity; and 
 based at least in part on the digital signal having the periodicity, generating the first injector signal, 
 wherein generating the second injector signal further comprises generating the second injector signal based at least in part on the digital signal having the periodicity and the track period measurement signal. 
 
     
     
       10. The method of  claim 7 , wherein estimating the amplitude of the track crossing speed signal further comprises:
 estimating a track period measurement signal, wherein the track period measurement signal indicates an error associated with tracking a plurality of tracks of the disc by the focusing apparatus of the disc drive system; and 
 based at least in part on the track period measurement signal, estimating the amplitude of the track crossing speed signal. 
 
     
     
       11. The method of  claim 7 , wherein:
 the disc drive system is an optical disc drive; 
 the disc is an optical disc; and 
 the focusing apparatus is a lens. 
 
     
     
       12. A controller of a disc drive system, the controller comprising:
 a position control module configured to oscillate a focusing apparatus of the disc drive system, based at least in part on a first injector signal; and 
 an eccentricity measurement module comprising
 a speed determination module configured to estimate an amplitude of a track crossing speed signal while the focusing apparatus is being oscillated and a disc placed within the disc drive system is being rotated, 
 an injector signal generation module configured to generate the first injector signal and a second injector signal, wherein the second injector signal has a frequency that is substantially the same as a frequency of the first injector signal, wherein the eccentricity measurement module is configured to, based at least in part on the estimated amplitude of the track crossing speed signal and the second injector signal, estimate a sign of the track crossing speed signal, 
 a multiplication module configured to
 receive a processed version of the amplitude of the track crossing speed signal and the second injector signal, and 
 generate a multiplication signal that is indicative of a sign of the track crossing speed signal, 
 
 a low pass filter configured to receive the multiplication signal and attenuate a high frequency component of the multiplication signal to generate a sign detection signal, and 
 a comparison module configured to compare the sign detection signal with zero, wherein an output of the comparison module provides an estimate of the sign of the track crossing speed signal. 
 
 
     
     
       13. The controller of  claim 12 , wherein the eccentricity measurement module further comprises an output module configured to:
 receive another processed version of the amplitude of the track crossing speed signal and the output of the comparison module; and 
 estimate an amplitude and a phase of an eccentricity signal that is indicative of an eccentricity in the rotation of the disc. 
 
     
     
       14. The controller of  claim 12 , wherein the position control module is configured to oscillate the focusing apparatus:
 with a frequency that is substantially higher than a frequency of rotation of the disc within the disc drive system; and 
 with an amplitude that is lower than a pitch of a track of the disc. 
 
     
     
       15. A controller of a disc drive system, the controller comprising:
 a position control module configured to oscillate a focusing apparatus of the disc drive system, based at least in part on a first injector signal; and 
 an eccentricity measurement module comprising
 a speed determination module configured to estimate an amplitude of a track crossing speed signal while the focusing apparatus is being oscillated and a disc placed within the disc drive system is being rotated, and 
 an injector signal generation module configured to generate the first injector signal and a second injector signal, wherein the second injector signal has a frequency that is substantially the same as a frequency of the first injector signal, wherein the eccentricity measurement module is configured to, based at least in part on the estimated amplitude of the track crossing speed signal and the second injector signal, estimate a sign of the track crossing speed signal, 
 
 wherein the track crossing speed signal comprises (i) a low frequency component that is substantially due to the eccentricity of the disc, and (ii) a high frequency component that is substantially due to the oscillation of the focusing apparatus, and 
 wherein the eccentricity measurement module further comprises a band pass filter configured to filter the track crossing speed signal such that an output of the band pass filter substantially comprises the high frequency component of the track crossing speed signal. 
 
     
     
       16. The controller of  claim 15 , wherein:
 the disc drive system is an optical disc drive; 
 the disc is an optical disc; and 
 the focusing apparatus is a lens. 
 
     
     
       17. A disc drive system comprising:
 a focusing apparatus; 
 a position control module configured to oscillate the focusing apparatus of the disc drive system, based at least in part on a first injector signal; and 
 an eccentricity measurement module comprising:
 a speed determination module configured to estimate an amplitude of a track crossing speed signal while the focusing apparatus is being oscillated and a disc placed within the disc drive system is being rotated, 
 an injector signal generation module configured to generate the first injector signal and a second injector signal, wherein the second injector signal has a frequency that is substantially the same as a frequency of the first injector signal, and 
 a multiplication module configured to:
 receive a processed version of the amplitude of the track crossing speed signal and the second injector signal, and 
 generate a multiplication signal that is indicative of a sign of the track crossing speed signal. 
 
 
 
     
     
       18. The disc drive system of  claim 17 , wherein the eccentricity measurement module further comprises:
 a low pass filter configured to receive the multiplication signal and attenuate a high frequency component of the multiplication signal to generate a sign detection signal; 
 a comparison module configured to compare the sign detection signal with zero, wherein an output of the comparison module provides an estimate of the sign of the track crossing speed signal; and 
 an output module configured to, based at least in part on the estimated amplitude and the estimated sign of the track crossing speed signal, estimate an eccentricity signal, wherein the eccentricity signal measures an eccentricity of the disc while the disc rotates within the disc drive system. 
 
     
     
       19. The disc drive system of  claim 17 , wherein in response to estimating the eccentricity signal, the focusing apparatus performs an acquisition and tracking of a track of the disc.